There is no IPv6 support in ZCS for Amavis at this time. It looks to me like "localhost" is returning the IPv6 addr before the IPv4 addr. You should just be able to change the order in your /etc/hosts file so that IPv4 is first.

There were no changes to the Amavis version between 7.0.1 and 7.1.1, so it is likely this is due to some other change you made on your server at the same time.